The Washington Nationals are interested in adding a starting pitcher and center fielder at the winter meetings, which begin Monday. The Nats are also said to be linked to first baseman Prince Fielder, who could be the second straight big ... more >

A Major League Baseball roster can be a fluid thing, never more than when the July 31 non-waiver trade deadline approaches each year.

The roster shifted for the Washington Nationals on Saturday when Jerry Hairston Jr. and Jason Marquis were dealt for minor leaguers in separate trades. And with less than 24 hours left until Sunday’s 4 p.m. EST deadline, a more significant re-working of the roster seemed likely.

“We’re on the cusp of making some changes to become the kind of club I know we can be,” manager Davey Johnson said. “There’s a lot of different contingency plans right now, a bunch of them. It just depends on which one we go to.”

One of those contingency plans is Twins center fielder Denard Span. He’s currently rehabbing with Triple-A Rochester from a concussion. And with Friday’s demotion of Roger Bernadina to Triple-A, the Nationals are left with Rick Ankiel as their everyday option in center field, an unlikely proposition for the remainder of the season.

The uncertainty that’s a hallmark of the trade deadline trickled into the Nationals’ clubhouse. Players were glued to smartphones and cocked their heads to watch ESPN update the trade market.

“It doesn’t really affect you too much,” said closer Drew Storen, mentioned as part of a deal for Span, “because you realize it’s part of it.”

That doesn’t mean the players are immune to the chatter. Scheduled to start Saturday against the New York Mets, Marquis hung around his locker in an odd scene, waiting to be officially told he was on his way to the Arizona Diamondbacks long after the news leaked. Until the news was delivered, Nationals’ officials insisted he was the starting pitcher and, as such, wouldn’t speak.

An anchor of Washington’s rotation, Marquis went 8-5 with a 3.95 ERA over 120 2/3 innings. The move saves the Nationals money, as Marquis is in the final season of a two-year, $15 million deal.

Baseball America didn’t rank Walters among Arizona’s top 10 prospects and, in a reaction to Saturday’s deal, projected a future as a utilityman.

But, Washington lost a utilityman Saturday morning, after it dealt Jerry Hairston Jr. to the Brewers. After second baseman Rickie Weeks injured his ankle (and is expected to be out from three-to-six weeks), Milwaukee was in need of a middle infielder.

Hairston’s versatility — he played five positions this season — helped the Nationals through Ryan Zimmerman’s early-season absence. He rolled up a .342 OBP in 75 games and was also a steadying influence in the clubhouse.

Erik Komatsu, a Double-A outfielder who heads to Harrisburg, came from the Brewers. Ranked the organization’s No. 14 prospect by Baseball America, Komatsu was the Brewers’ minor league player of the year in 2010.

But those weren’t the sort of roster-rocking moves Johnson hinted at Saturday.

Storen and fellow reliever Tyler Clippard’s names have popped up in many of the larger trade discussions.